The present invention relates generally to a zoom lens and an imaging apparatus incorporating the same, and more particularly to a zoom lens of small format that lends itself to imaging apparatus inclusive of video cameras and digital cameras.
In recent years, imaging apparatus such as digital cameras designed to take images of subjects using solid-state imaging devices such as CCDs or CMOSs have gone mainstream in place of silver-halide film cameras. Further, they have now a wide spectrum of categories from the commercial high-end type to the compact low-end type. The present invention gives weight to the compact low-end type category in particular.
Users of such low-end type digital cameras would enjoy snapping shots over a wide range of scenes at any time in any place. For this reason, preference is given to small-format digital cameras, especially of the type that can be well put away in the pockets of clothing or baggage, are convenient to carry around, and are slimmed down in their thickness direction, and there is a mounting demand for size reductions of taking lens systems, too.
On the other hand, as the pixels of imaging devices are now on the increase, there is a mounting demand for higher optical performance keeping pace with a lot more pixels. Further, to make sure mass productivity, it is required to minimize the sensitivity of optical performance deterioration to production errors in the process of processing and assembling lenses. From the point of view of making taking ranges wide, high zooming lenses having zoom ratios exceeding 5 or 7, too, are generally available; much higher zoom ratios are expected, and so are wider-angle arrangements. To meet such demands, there are now various types of zoom lenses proposed in the art.
Among prior zoom lenses having relatively high zoom ratios and compact format adapted to shift some lens groups to receive or put away them in a lens mount, there is a type comprising, in order from its object side, a first lens group of positive refracting power, a second lens group of negative refracting power, a third lens group of positive refracting power and a fourth lens group of positive refracting power, as set forth in the following patent publication 1.
[Patent Publication 1]
JP(A)2006-330657
Problems with the zoom lens put forward in Patent Publication 1 are, however, that the volume of the whole unit grows too large for size reductions, because of an increased amount of shift of the third lens group at the time when a lens barrel is receive in the lens mount.
The invention has been made to meet the users demands for making taking ranges wider than ever before without detrimental to the ability of cameras to be carried around: the invention has for its object the provision of a less costly zoom lens that satisfies the requirements of making cameras smaller and having high zoom ratios and wide-angle arrangements at the same time, enables the image quality of taken images to be well kept, and lends itself to imaging devices such as CCDs or CMOSs as well as electronic imaging apparatus incorporating the same.